| Main Ref. | Trewavas, E., 1983 |
| Appearance refers to | Male; Female |
| Bones in OsteoBase |
| Specialized organs | genital papilla with tassels (m) |
| Different appearance | different morphology during breeding season only |
| Different colors | different colors during breeding season only |
| Remarks | Male with bifid white genital tassel (Ref.4967); with blue or white head while female/juvenile silver grey (Ref. 6150). Ripe testes broad, white & sinuous. |
| Striking features | none |
| Body shape lateral | fusiform / normal |
| Cross section | compressed |
| Dorsal head profile | more or less straight |
| Type of eyes | more or less normal |
| Type of mouth/snout | more or less normal |
| Position of mouth | terminal |
| Type of scales | cycloid scales |
| Diagnosis |
Diagnosis: A heavily-built large tilapia species with a wide rounded head; dwarf populations exist in some crater lakes, showing bony 'hunger-form' body shape (Ref. 118638). Females and juveniles with grey bodies and 6 or more vertical bars; males have a bright blue, occasionally white or green, 'mask' across the head; when fully ripe, the underside of most of the body can be black, with the upper surface a conspicuous white to pale blue; genital tassel can be long and branched, pinkish to bright yellow; females and non-territorial males are indistinguishable from Oreochromis karongae (Ref. 118638). Description: Length of head35.7-38.0% of standard length; lower pharyngeal toothed area with concave sides; median length of bone 1.26-1.36 times its width and 37.6-40.6% length of head; blade 1.6-2.4 times the median length of the toothed area; length of lower jaw 31.4-34.0% length of head; teeth of jaws in 3-5 rows (Ref. 2). Colouration: Breeding male silvery blue with white and pale blue top of head and dorsum and white dorsal margin (Ref. 2). |
| Ease of Identification |
| Lateral Lines | 2 Interrupted: No |
| Scales on lateral line | 32 - 35 |
| Pored lateral line scales | |
| Scales in lateral series | |
| Scale rows above lateral line | |
| Scale rows below lateral line | |
| Scales around caudal peduncle | |
| Barbels | 0 |
| Gill clefts (sharks/rays only) | absent |
| Gill rakers | |
| on lower limb | 17 - 22 |
| on upper limb | 2 - 4 |
| total | |
| Vertebrae | |
| preanal | |
| total |
| Attributes | extending over most of the back length |
| Fins number | 1 |
| Finlets No. | Dorsal |
| Ventral | |
| Spines total | 16 - 17 |
| Soft-rays total | 10 - 11 |
| Adipose fin | absent |
| Attributes | more or less truncate; more or less normal |
| Fins number | 1 |
| Spines total | 3 - 3 |
| Soft-rays total | 8 - 10 |
| Pectoral | Attributes more or less normal |
| Spines | |
| Soft-rays | |
| Pelvics | Attributes more or less normal |
| Position thoracic beneath origin of D1 | |
| Spines | |
| Soft-rays |